Portable power saw guide for mitre cuts and the like



6-47, 47-6. 6, s9; 83/(lnquired) 1 v i United States Patent 1 1 3,543,816

12 Inventor [56] References cm email" UNITED STATES PATENTS A,PPL 1.911,o4s 5/1933 Tinnen 143 6 I221 d mo 2,396,961 3/1946 Meredith 143/6 t 2 2,823,709 2/1958 Konieczka l43/6 Primary Examiner-Donald R. Schran Attorney-Edwin M. Thomas I a ABSTRACT: A guide or adapter for portable power saws is designed to rest on and lock to the timber to be cut in order to [.54] 'ORTAM SAW GUIDE R MTRE facilitate cutting structural elements that are used in quantity CUTS AND LIKE in construction, such as rafters, for example. It comprises a 7 cmvs saw base adapter and an adjustable protractor and guide arm [52] U.S.Cl. 143/6. or track for the saw with quiclerelease adjustable clamping 143/89 means for engaging the timber to becut. The clamping-means [5 I] I... (L 827!) 27/06 is designed to'hold firmly to timbers of moderate dimensions [50] Field of 143/6-43, or tolerances without readj stment and the saw can slide freely on and off the guide track.

1. PORTABLE POWER sAw GUIDE FOR MITRE CUTS AND TIIE LIKE BACKGROUND AND PRIOR ART A need has long been recognized for a simple and instantly detachable device for mechanically guiding a manually operated power saw so that a relatively unskilled carpenter can perform work of good quality. An early example is shown in U.S. Pat. No. 1,540,388. In such operations as'cutting rafters, manualor portable power saws either have hat been used very successfully by most operators or the work quality has been poor. A number of devices have been proposed to convert portable power saws to bench or table saws, in order to cut timbers along desired lines. In general'these have not been as successful as might be desired, and they are mechanically complex, and not versatile. In U.S. Pat. No. 2,620,835, for example, a saw guide is attached to a table or platform and can be adjusted angularly. See also U.S. Pat. Nos. 2,630,146, 2,718,907, and 2,903,026. Such devices can be used to make transverse cuts at a desired angle in a main plane of the timber. Devices of this type, however, usually require that the timberto be cut'be held manually against a guide or stop element, which is oftendifficulLlf the timber is not accurately and firmly held, the angle of cut, of course, will not be true. Furthermore, in most of these devices there is no provision for cutting in a plane other than perpendicular to a main face of the timber. Inaccurate'angles, especially at the apex and hip joints or rafters, greatly reduce structural strength.

Various types of jigs have been proposed, as in U.S. Pat. No. 2,876,808, for holding timbers or guiding saws while various types of cuts are made. In some cases elaborate apparatus is suggested for resting on a support such as a pair of saw horses. For example, an apparatus as in U.S. Pat. No. 2,994,351, is secured to a heavy timber. It has means for positioning saws or marking cuts at various points, e.g. to out the ridge end of a rafter, cut a notch as the wall plate end, etc. It is highly desirable, for applicants purpose, to keep the saw guide simple, light in weight, and directly attachable to the rafter which is to be cut to avoid use of tables and other special supports. This is not possible with most of the devices described above. Socalled radial arm saws are heavy, and, as a rule, the work must be brought to them.

Various devices have been proposed for, in effect, converting portable power saws to radial arm types (nonportable). These have various advantages for many purposes but they still require that the work be brought to the saw; hence, they are not entirely suitable for the purposes of the present inventIon.

Particular objects of the present invention are to make it possible to convenient to:

a. use the timber itself as the basic support for the saw and ,the guide that is designed to control the saw;

b. attach the saw to a simple slidable base which is easily removable and slidable and guidable on a simple, accurate, and lightweight straight track element attachable by quick release means to the timber to be cut;

c. adjust theguide to any desired cutting angle in the plane of a main face of the timber;

d. independently adjust the saw on its own base to cut any desired angle with respect to said plane of a main face while remaining under control of the guide; e. positively and quickly secure the guide successively to the timbers to be cut, even though these timbers may vary somewhat in dimensions;

f. produce a series of structural elements, with identical cuts in rapid succession with very simple equipment.

There are important advantages in using the timber itself as a basic guide and support for the saw. No workbench or other baseis needed. The timber to be cut can be laid across a pair of sawhorses, or one end may rest on the floor or ground and the other on a horse or other support. Most commercial saws need no modification other than (possibly) drilling a plurality of holes in the normal base plates, and attaching a guide plate.

This guide plate can be left on the saw, for most normal uses of the saw, without interference, but it can be quickly removed. Y

if desired. The guide plate or auxiliary adapter baseis designed to slide along a simple but highly accurate guide track which is formed as to retain the saw against any displace mentor misalinement during the cut.

Most, if not all, commercial hand-controlled power saws are adjustable with respect to their own bases which support the saw proper. Hence, the plane of the saw blade can be.readily changed, e.g. to a 45 angle, as distinguished from the normal minimal misalinement due to carelessness, and no bad angle cuts because of failure to hold the timber firmly against a guide or to hold a guide and the attached saw firmly against the timber. When the cut is finished, the guide, which is light in weight, andthe saw are released and lifted off as a unit for placement on and clamping to the next timber. The clamping device is readily adjustable to fit 2X4, 2X6, 2X8and other timbers of standard or conventional sizes and can be fitted 'to irregular timbers if necessary, withoutsubstantial modification. The saw, of course, should have adequate cutting depth to cut all the way through the timber at the desired angle. v,

While'particular reference'has been made above to cutting rafters, which commonly involve quite a lot of skilled l'abor, the invention is equally useful for making square end, mitre, or

other angular cuts on large moldings, trim boards, as well as joists, studding, and other structural members used in quantity in the building trades. Obviously, it can be used also for cutting of flooring, frames, and othcrelements. The normal guide is made'long-enough for cutting'timbers of the most common widths; however,'by using a guide of suitable length, this invention can be used for cutting wider doors, trimming window sash, etc. Other uses and advantages will appear or will be obvious to those skilled in the art from the detailed description given below.

BRIEF DESCRIPTION OF DRAWINGS I FIG.'1 shows a perspective view of a preferred embodiment with the saw omitted.

FIG. 2 shows a sectional view of the saw substantially along line 2-2 of FIG. 1.

FIG. 3 shows a sectional view at a different angle, of the guide track, taken I workgripping or clamping mechanism, taken substantially 1 along line 3-3 of FIG. 1.

FIG. 4 shows a view, illustrating how a conventional portable power saw is set on the guide track where it can be moved along the track, which can be adjusted to various angles with respect to the work timber and the clamping mechanism.

FIG. 5 is a bottom view showing the adapter or auxiliary base secured to the conventional bottom plate or base of a conventional saw.

DESCRIPTION OF PREFERRED EMBODIMENT The plate 13 is adapted to lie on the top face of timber 11 and lar guide brackets 18 and 19. These are adapted to receive in smooth sliding fit and for parallel movement a pair of rods 20, 21, respectively attached firmly to ears 22, 23 of a rectilinearly movable clamp supporting bar 24. A smooth clamping plate 25 is attached to clamp bar 24 through rods 26, 27, which are fixed to the ears 22 and 23, respectively, eg by set screws S. Through a resilient strip 28 of rubber or equivalent elastic material, a clamp bar 29 of wood, preferably faced with metal 30, is adapted to be forced into clamping engag'ement with the rear side of the timber 11. The timber thus is gripped snugly and firmly between flange l5 and bar 29, 30. Resilient strip 28 permits the clamp to grip timbers of slightly varying widths without special or individual adjustment, to accommodate the usual tolerances'in saw mills and planers,

and/or to accommodate timbers which vary. moderately in transverse dimensions due, for" example,,.,tovariations in moisture contenL'Themetal element 30 is not essential in all cases but the clamp bar 29;should have .-its timber engaging face true and solid so as to grip the piece 11 firmly but without objectionable marring. The face of member 29 (or 30) and/or the inside surface of flange 15 may be lightly grooved or knurled to improve the grip, if desired. Normally, this is not necessary.

A bifurcate lever 32, FIG. 1, is pivoted at its ends 33, 34 to the twobrackets l8 and l9..At a short distance from these end pivots, a pair of links 35, 3 6 are pivotally attached at 37, 38, one of each arm of the bifurcate lever. The opposite ends of these links are pivotally attached to a transverse bar or shaft 39. Bar or shaft 39 is mounted at its ends in a pair of blocks 40, 4] adjustable secured to guide rods and 21, respectively. Set screws 42 can. be loosened and reset to adjust the clamp for timbers of different widths. Separate pins can replace bar 39 if desired.

These adjustment means are arranged so that the clamp elements l5 and 30 will grip any reasonably standard two-byfour, two-by-six or other timber without regard to minor variations in timber width. The resilient strip 28 permits this. There is also, of course, some slight resilience in the clamping mechanism, aside from strip 28, which allows some small tolerance. In this way it is a simple matter to change the width of the clamp system for substantially different timber widths, while it is'unnecessary to adjust from timber to timber to accommodate minor variations.

The ears 22 23 also may be secured adjustably to rods 20, 21 by means of set screws 28, 29, if desired, In this case, the links 35and 36 can be permanently attached to'the guide rods 20 and 21. The arrangement shown is presently preferred, however. When the bifurcate lever 32, FIG. 1, is pulled forward to or slightly past dead center for pivot points 34, 35 with respect to pivots 30, it acts as a powerful toggle to move the guide rods and the clamp'member per se to clamping position and thus the device is firmly clamped to the timber.

The main support member 13 is secured to or, if preferred, may be made integral with an ear-shapedextension or bearing base 51. The latter, as best seen in FIG. 4, supports on a large diameter bronze bearing 53 arotatably mounted protractor plate or disc element 55-.The arrangement is such that the bronze bearing is of the samethickness as the element 55 .so

protruding tongue elements on each lateral edgesTrack 58- I may be machined from a simple piece of stock, or.alternatively. it may be made up of laminations'59, 60,61 of which the upper and lower elements 59 and 61 are .slightlynarrower that lines. The bar 58,unitary of composite, serves as a guide track for a simple base plate adapter 62. Adapter 62, of which a bottom view is shown-in H6, 5, attaches to a conventional saw 7 base plate 63. it has a pair of spaced parallel grooved guide bars 64, 65, FIG. 5, which engage the tongue elements T mentioned above. These tongue and groove elementsT, etc., act as slideways to keep the baseplate adapter 62 running true and in a straight line. The-saw 100 is secured'to its-own base plate 63 and, of course, is constrained to travel in a straight U line when adapter base 62'is-placed on the guide trackmThe saw can be slid freely off the end of thetrack whenever the operator wants to use it for some other purpose but it cannot:-

be raised off the track while cutting. The attached adapter-62 is light in weight and only a small fraction of an inch in thickness. It does not interfere with normal use of the saw. it is attached by countersunk screws 6'6 an'd"nu ts 67, which can be plane of the saw blade B in any desired adjusted angle. A set screw or equivalent normally is adapted to be tightened against the sector 77 to hold the parts in the desired position of adjustment. With this arrangement, the saw may be adjusted in angular position with respect to a plane normal to the top face of the timber. For simple rafters, cutting off the ends of joists, studding, etc., the saw is essentially perpendicular to surface plane of the work, as will most commonly be required; however, for cutting the upper ends of jack ra fters, or of hip rafters, etc., this angle can be changed and the saw set to an appropriate angle, such as 45, as shown in dotted lines 74, FIG. 2. The protractor angle, as determined-by arcuate arm 82, fixed to base plate 57 and concentric with protractor disc 55, is set appropriately by the parts next to be described.

The saw 100, H6. 4, which, of course, is no'part of the present invention, is driven by conventional motor means 101 (and may include gear reduction means). Electric current is supplied through a cord 102 and the operating handle 103 is of conventional type. The saw generally has a conventional safety guard 104, the lower part of which may be retracted while the machine is operated, as is common practice.

The arcuate arm of protractor index 82 on the saw guide it self is concentric with the bronze bearing 53 and disc 55 and indicates the angle to be cut with respect toan edge of the timber. A clamp screw 84 is set in a slotted or undercut guide plate 83. When tightened against arm 82, this screw holds the parts at the desi ed angle. Once the device has been set, as many rafters or other parts may be cut as desired by simply clamping the unit to each timber in turn, turning on the saw motor, and pushing the saw along guide track 58, with the tonque elements T engaged by base adapter 62 as described above. Cap 54 is secured by nuts on adjustable screws 56 tapped in bearing 53 with their heads smoothly countersunk into base 51 and holds these partsin snug frictional fitting relationship.

In using the apparatus of this invention, the carpenter first adjusts the clamp to fit the timber by loosening set screws 42 (or 28', 29, if preferred), sliding the clamp bar 29, 30, to appropriate position and retightening. The clamp should fit tightly but not so tight as to mar or deform the timber. The resilient rubber'strip 28 should be partly, but not completely, compressed. Then he sets the protractor arm 82 to the desired angle, by loosening and resetting the screw 84: The base adapter 62 is attached to the saw base 6 3b y screws 66, if not already secured to it, and the appropriate angle for the saw cutis set on the saw protractor 77. g

The saw adapter base is then slid onto the outer end 96 of .the track member 58. The saw motor is turned on and the saw slid along the track, which it must follow until the cut is complete,;unl ess the saw is withdrawn in the reverse direction.

As a rule thesaw will be withdrawn from track 58 before the guide device is unclamped from the timber by raising bifurcate lever 32 and shifted to another piece to be cut.

smooth operation; hence, guides such as rods 20, 21, and their receivers 18 and 19 are preferred, but other obvious arrangements can be used. If desired, compression springs may be mounted in the guides 18 and 19 and arranged to draw the clamp bar 24 snugly against the timber, in which case the lever 27, preferably bifurcate but which may be single in some cases, is operated only to release the clamp from the timber, i.e. to open it for application to a new timber. The guide member which attaches to the saw is complementary to the guide rail 58, which may have other sectional shapes or configurations then those shown, e.g. it may be provided with a T- slot etc., with appropriate followers or tracking elements being provided on the saw base or adapter 63. The whole guiding apparatus is relatively very light in weight. It is sturdy and reliable and gives perfect guidance to the saw. Besides insuring accurate cutting it also reduces greatly any danger of injury to an inexperienced saw operator,

Various parts of the apparatus may be changed or modified, as will be evident to those skilled in the art, without departing from the spirit, purpose or principles of the invention.

It is intended by the claims which follow to cover the foregoing, and other obvious variations, modifications and combinations, as broadly as the prior art properly permits.

Iclaim:

l. -A control device and guide for portable power saws, adapted to be secured to and supported by a timber to be cut, comprising, in combination, a rigid base member having a plane surface adapted to engage and lie flat on a timber surface, said base member having also a rigid side flange disposed at a right angle to said plane surface and adapted to serve as one element of a clamp for said timber, spaced parallel guide means secured to said base, and extending transversely thereon with respect to said flange, parallel clamp-supporting elements adapted to move under guidance of said guide means to clamping and nonclamping positions, respectively, a second clamp element carried by and adjustable with respect to said parallel supporting elements and adapted on movement of said elements to engage a surface of said timber opposite the flange for clamping in firmly, clamp-operating means pivoted to said base and connected to said elements, an elongated saw guide, bearing means securing said saw guide pivotally to said base, indicator means for showing angular relationship between said guide and said base, means for holding the saw guide in a selected angular relationship with respect to the base, means on the saw guide for holding a portable saw in a constrained path of travel for cutting in a plane transverse to said timber, and an adapter attachable to said saw and fitted to the saw guide for keeping the saw on said guide during a cutting operation.

2. Combination according to claim 1 wherein the saw guide comprises a track element having a protruding tongue element on each side thereof, and the adapter is formed with grooves to receive said tongue elements in sliding relationship.

3. Construction according to claim 1 wherein the adapter comprises a track element which is open ended and on which the adapter is slidable and fully withdrawable from said track element,

4. Combination according to claim 1 in which the saw guide has a pair of undercut surfaces and the adapter has complementary elements for preventing removal of the saw by lifting from the guide during a cutting operation.

5. Combination according to claim 1 in which the second clamp element includes a rigid backing bar, a timber-engaging bar and a resilient layer of material between said bars.

6. Combination according to claim I in which the clampoperating means comprises an overcenter toggle lever.

7. Combination according to claim 1 in which the guide is mounted to the base member without play through a snugly fitting friction bearing. 

